In recent years, in the art of photomechanical process, it has been desired to use a photographic light-sensitive material excellent in original reproducibility and a processing system which can operate with reduced amount of waste liquid to be disposed so as to cope with diversification and complexity of printed matters and the rise in environmental awareness.
In order to obtain good reproduction of a halftone image in continuous gradation or of a line work, an image formation system exhibiting an ultrahigh contrast (particularly having a .gamma. value of 10 or more) photographic property is required.
For forming a high contrast image, a lithographic development system employing a so-called "infectious development effect" has been commonly used. However, this lithographic development system is disadvantageous in that the developer is too unstable to be used. An image forming system has been desired in which the photographic light-sensitive material is developed with a processing solution having a good storage stability to obtain an ultrahigh contrast. Examples of such an image forming system are disclosed in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,269,922, 4,272,606, 4,311,781, 4,332,878, 4,618,574, 4,634,661, 4,681,836 and 5,650,746. In this image forming system, a surface latent image type silver halide photographic material comprising a hydrazine derivative incorporated therein is developed with a stable MQ or PQ developer having a pH value of from 11.0 to 12.3 to obtain an ultrahigh negative image having .gamma. of more than 10. In accordance with this process, an ultrahigh contrast and a high photographic sensitivity can be obtained. Further, a sulfite can be added to the developer in a high concentration. Accordingly, the developer thus obtained exhibits a remarkably improved stability against air oxidation as compared with the conventional lith developers.
The above described methods make it possible to use a high concentration sulfite preservative to enhance the stability of the developer. However, in order to obtain an ultrahigh contrast photographic image, it is necessary that a developer having a relatively high pH value be used. Such a developer having a relatively high pH value is liable to air oxidation. Thus, it is necessary that the developer be replenished at a high rate. Therefore, some means have been elaborated in an attempt to realize an ultrahigh contrast photographic image forming system comprising the nucleation development with a hydrazine compound by using a developer having a lower pH value.
U.S. Pat. Nos. 4,269,929 (corresponding to JP-A-61-267759 (The term "JP-A" as used herein means an "unexamined published Japanese patent application")), 4,737,452 (corresponding to JP-A-60-179734), 5,104,769, 4,798,780, 4,998,604 and 4,994,365, JP-A-1-179939 and JP-A-1-179940 disclose a process which comprises the use of a hydrazine nucleating agent having high activity and a nucleation accelerator in order to obtain an ultrahigh image with a stable developer having a pH value of less than 11.0. These publications also disclose that a chemically-sensitized silver halide emulsion having a high silver chloride content also has a high nucleation activity. However, this process is disadvantageous in that the developer needs to be replenished at a rate of from 320 to 450 ml per m.sup.2 of silver halide photographic material to be processed. Further enhancement of the processing stability of the system has been desired.
The use of such a highly active hydrazine nucleating agent is disadvantageous in that a sand-like fog called black pepper tends to occur in the unexposed areas or that the photographic light-sensitive material is sensitized more than desired when aged under natural conditions.
Further, the use of the above described highly active hydrazine nucleating agent is disadvantageous in that when the emulsion layer coating solution containing such a hydrazine nucleating agent is aged in the form of solution, sensitization is effected vigorously, raising some problems in productivity.
The incorporation of a hydrazine compound in the coating solution in the form of solid dispersion is disclosed in JP-A-2-3033, JP-A-7-175159 and JP-A-4-102848. However, the techniques disclosed therein cannot solve the above described problems.
Further, the use of such a highly active nucleating agent is disadvantageous in that the nucleating agent in the photographic light-sensitive material is decomposed more rapidly than desired with the lapse of time during natural aging, giving a great adverse effect on photographic properties. JP-A-7-175159 discloses that a hydrazine compound is incorporated in a coating solution in the form of solid dispersion and an amino compound is incorporated in the photographic light-sensitive material as a nucleation accelerator. However, such an amino compound accelerates the decomposition of the nucleating agent, and thus the above described problems are worsened.